# Copyright 2015 The TensorFlow Authors. All Rights Reserved.
#
# Licensed under the Apache License, Version 2.0 (the "License");
# you may not use this file except in compliance with the License.
# You may obtain a copy of the License at
#
#     http://www.apache.org/licenses/LICENSE-2.0
#
# Unless required by applicable law or agreed to in writing, software
# distributed under the License is distributed on an "AS IS" BASIS,
# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
# See the License for the specific language governing permissions and
# limitations under the License.
# ==============================================================================
# pylint: disable=invalid-name
"""ResNet models for Keras.

Reference:
  - [Deep Residual Learning for Image Recognition](
      https://arxiv.org/abs/1512.03385) (CVPR 2015)
"""
from __future__ import absolute_import
from __future__ import division
from __future__ import print_function

import tensorflow.compat.v2 as tf

from keras import backend
from keras.applications import imagenet_utils
from keras.engine import training
from keras.layers import VersionAwareLayers
from keras.utils import data_utils
from keras.utils import layer_utils
from tensorflow.python.util.tf_export import keras_export


BASE_WEIGHTS_PATH = (
    'https://storage.googleapis.com/tensorflow/keras-applications/resnet/')
WEIGHTS_HASHES = {
    'resnet50': ('2cb95161c43110f7111970584f804107',
                 '4d473c1dd8becc155b73f8504c6f6626'),
    'resnet101': ('f1aeb4b969a6efcfb50fad2f0c20cfc5',
                  '88cf7a10940856eca736dc7b7e228a21'),
    'resnet152': ('100835be76be38e30d865e96f2aaae62',
                  'ee4c566cf9a93f14d82f913c2dc6dd0c'),
    'resnet50v2': ('3ef43a0b657b3be2300d5770ece849e0',
                   'fac2f116257151a9d068a22e544a4917'),
    'resnet101v2': ('6343647c601c52e1368623803854d971',
                    'c0ed64b8031c3730f411d2eb4eea35b5'),
    'resnet152v2': ('a49b44d1979771252814e80f8ec446f9',
                    'ed17cf2e0169df9d443503ef94b23b33'),
    'resnext50': ('67a5b30d522ed92f75a1f16eef299d1a',
                  '62527c363bdd9ec598bed41947b379fc'),
    'resnext101':
        ('34fb605428fcc7aa4d62f44404c11509', '0f678c91647380debd923963594981b3')
}

layers = None


def ResNet(stack_fn,
           preact,
           use_bias,
           model_name='resnet',
           include_top=True,
           weights='imagenet',
           input_tensor=None,
           input_shape=None,
           pooling=None,
           classes=1000,
           classifier_activation='softmax',
           **kwargs):
  """Instantiates the ResNet, ResNetV2, and ResNeXt architecture.

  Args:
    stack_fn: a function that returns output tensor for the
      stacked residual blocks.
    preact: whether to use pre-activation or not
      (True for ResNetV2, False for ResNet and ResNeXt).
    use_bias: whether to use biases for convolutional layers or not
      (True for ResNet and ResNetV2, False for ResNeXt).
    model_name: string, model name.
    include_top: whether to include the fully-connected
      layer at the top of the network.
    weights: one of `None` (random initialization),
      'imagenet' (pre-training on ImageNet),
      or the path to the weights file to be loaded.
    input_tensor: optional Keras tensor
      (i.e. output of `layers.Input()`)
      to use as image input for the model.
    input_shape: optional shape tuple, only to be specified
      if `include_top` is False (otherwise the input shape
      has to be `(224, 224, 3)` (with `channels_last` data format)
      or `(3, 224, 224)` (with `channels_first` data format).
      It should have exactly 3 inputs channels.
    pooling: optional pooling mode for feature extraction
      when `include_top` is `False`.
      - `None` means that the output of the model will be
          the 4D tensor output of the
          last convolutional layer.
      - `avg` means that global average pooling
          will be applied to the output of the
          last convolutional layer, and thus
          the output of the model will be a 2D tensor.
      - `max` means that global max pooling will
          be applied.
    classes: optional number of classes to classify images
      into, only to be specified if `include_top` is True, and
      if no `weights` argument is specified.
    classifier_activation: A `str` or callable. The activation function to use
      on the "top" layer. Ignored unless `include_top=True`. Set
      `classifier_activation=None` to return the logits of the "top" layer.
      When loading pretrained weights, `classifier_activation` can only
      be `None` or `"softmax"`.
    **kwargs: For backwards compatibility only.

  Returns:
    A `keras.Model` instance.
  """
  global layers
  if 'layers' in kwargs:
    layers = kwargs.pop('layers')
  else:
    layers = VersionAwareLayers()
  if kwargs:
    raise ValueError('Unknown argument(s): %s' % (kwargs,))
  if not (weights in {'imagenet', None} or tf.io.gfile.exists(weights)):
    raise ValueError('The `weights` argument should be either '
                     '`None` (random initialization), `imagenet` '
                     '(pre-training on ImageNet), '
                     'or the path to the weights file to be loaded.')

  if weights == 'imagenet' and include_top and classes != 1000:
    raise ValueError('If using `weights` as `"imagenet"` with `include_top`'
                     ' as true, `classes` should be 1000')

  # Determine proper input shape
  input_shape = imagenet_utils.obtain_input_shape(
      input_shape,
      default_size=224,
      min_size=32,
      data_format=backend.image_data_format(),
      require_flatten=include_top,
      weights=weights)

  if input_tensor is None:
    img_input = layers.Input(shape=input_shape)
  else:
    if not backend.is_keras_tensor(input_tensor):
      img_input = layers.Input(tensor=input_tensor, shape=input_shape)
    else:
      img_input = input_tensor

  bn_axis = 3 if backend.image_data_format() == 'channels_last' else 1

  x = layers.ZeroPadding2D(
      padding=((3, 3), (3, 3)), name='conv1_pad')(img_input)
  x = layers.Conv2D(64, 7, strides=2, use_bias=use_bias, name='conv1_conv')(x)

  if not preact:
    x = layers.BatchNormalization(
        axis=bn_axis, epsilon=1.001e-5, name='conv1_bn')(x)
    x = layers.Activation('relu', name='conv1_relu')(x)

  x = layers.ZeroPadding2D(padding=((1, 1), (1, 1)), name='pool1_pad')(x)
  x = layers.MaxPooling2D(3, strides=2, name='pool1_pool')(x)

  x = stack_fn(x)

  if preact:
    x = layers.BatchNormalization(
        axis=bn_axis, epsilon=1.001e-5, name='post_bn')(x)
    x = layers.Activation('relu', name='post_relu')(x)

  if include_top:
    x = layers.GlobalAveragePooling2D(name='avg_pool')(x)
    imagenet_utils.validate_activation(classifier_activation, weights)
    x = layers.Dense(classes, activation=classifier_activation,
                     name='predictions')(x)
  else:
    if pooling == 'avg':
      x = layers.GlobalAveragePooling2D(name='avg_pool')(x)
    elif pooling == 'max':
      x = layers.GlobalMaxPooling2D(name='max_pool')(x)

  # Ensure that the model takes into account
  # any potential predecessors of `input_tensor`.
  if input_tensor is not None:
    inputs = layer_utils.get_source_inputs(input_tensor)
  else:
    inputs = img_input

  # Create model.
  model = training.Model(inputs, x, name=model_name)

  # Load weights.
  if (weights == 'imagenet') and (model_name in WEIGHTS_HASHES):
    if include_top:
      file_name = model_name + '_weights_tf_dim_ordering_tf_kernels.h5'
      file_hash = WEIGHTS_HASHES[model_name][0]
    else:
      file_name = model_name + '_weights_tf_dim_ordering_tf_kernels_notop.h5'
      file_hash = WEIGHTS_HASHES[model_name][1]
    weights_path = data_utils.get_file(
        file_name,
        BASE_WEIGHTS_PATH + file_name,
        cache_subdir='models',
        file_hash=file_hash)
    model.load_weights(weights_path)
  elif weights is not None:
    model.load_weights(weights)

  return model


def block1(x, filters, kernel_size=3, stride=1, conv_shortcut=True, name=None):
  """A residual block.

  Args:
    x: input tensor.
    filters: integer, filters of the bottleneck layer.
    kernel_size: default 3, kernel size of the bottleneck layer.
    stride: default 1, stride of the first layer.
    conv_shortcut: default True, use convolution shortcut if True,
        otherwise identity shortcut.
    name: string, block label.

  Returns:
    Output tensor for the residual block.
  """
  bn_axis = 3 if backend.image_data_format() == 'channels_last' else 1

  if conv_shortcut:
    shortcut = layers.Conv2D(
        4 * filters, 1, strides=stride, name=name + '_0_conv')(x)
    shortcut = layers.BatchNormalization(
        axis=bn_axis, epsilon=1.001e-5, name=name + '_0_bn')(shortcut)
  else:
    shortcut = x

  x = layers.Conv2D(filters, 1, strides=stride, name=name + '_1_conv')(x)
  x = layers.BatchNormalization(
      axis=bn_axis, epsilon=1.001e-5, name=name + '_1_bn')(x)
  x = layers.Activation('relu', name=name + '_1_relu')(x)

  x = layers.Conv2D(
      filters, kernel_size, padding='SAME', name=name + '_2_conv')(x)
  x = layers.BatchNormalization(
      axis=bn_axis, epsilon=1.001e-5, name=name + '_2_bn')(x)
  x = layers.Activation('relu', name=name + '_2_relu')(x)

  x = layers.Conv2D(4 * filters, 1, name=name + '_3_conv')(x)
  x = layers.BatchNormalization(
      axis=bn_axis, epsilon=1.001e-5, name=name + '_3_bn')(x)

  x = layers.Add(name=name + '_add')([shortcut, x])
  x = layers.Activation('relu', name=name + '_out')(x)
  return x


def stack1(x, filters, blocks, stride1=2, name=None):
  """A set of stacked residual blocks.

  Args:
    x: input tensor.
    filters: integer, filters of the bottleneck layer in a block.
    blocks: integer, blocks in the stacked blocks.
    stride1: default 2, stride of the first layer in the first block.
    name: string, stack label.

  Returns:
    Output tensor for the stacked blocks.
  """
  x = block1(x, filters, stride=stride1, name=name + '_block1')
  for i in range(2, blocks + 1):
    x = block1(x, filters, conv_shortcut=False, name=name + '_block' + str(i))
  return x


def block2(x, filters, kernel_size=3, stride=1, conv_shortcut=False, name=None):
  """A residual block.

  Args:
      x: input tensor.
      filters: integer, filters of the bottleneck layer.
      kernel_size: default 3, kernel size of the bottleneck layer.
      stride: default 1, stride of the first layer.
      conv_shortcut: default False, use convolution shortcut if True,
        otherwise identity shortcut.
      name: string, block label.

  Returns:
    Output tensor for the residual block.
  """
  bn_axis = 3 if backend.image_data_format() == 'channels_last' else 1

  preact = layers.BatchNormalization(
      axis=bn_axis, epsilon=1.001e-5, name=name + '_preact_bn')(x)
  preact = layers.Activation('relu', name=name + '_preact_relu')(preact)

  if conv_shortcut:
    shortcut = layers.Conv2D(
        4 * filters, 1, strides=stride, name=name + '_0_conv')(preact)
  else:
    shortcut = layers.MaxPooling2D(1, strides=stride)(x) if stride > 1 else x

  x = layers.Conv2D(
      filters, 1, strides=1, use_bias=False, name=name + '_1_conv')(preact)
  x = layers.BatchNormalization(
      axis=bn_axis, epsilon=1.001e-5, name=name + '_1_bn')(x)
  x = layers.Activation('relu', name=name + '_1_relu')(x)

  x = layers.ZeroPadding2D(padding=((1, 1), (1, 1)), name=name + '_2_pad')(x)
  x = layers.Conv2D(
      filters,
      kernel_size,
      strides=stride,
      use_bias=False,
      name=name + '_2_conv')(x)
  x = layers.BatchNormalization(
      axis=bn_axis, epsilon=1.001e-5, name=name + '_2_bn')(x)
  x = layers.Activation('relu', name=name + '_2_relu')(x)

  x = layers.Conv2D(4 * filters, 1, name=name + '_3_conv')(x)
  x = layers.Add(name=name + '_out')([shortcut, x])
  return x


def stack2(x, filters, blocks, stride1=2, name=None):
  """A set of stacked residual blocks.

  Args:
      x: input tensor.
      filters: integer, filters of the bottleneck layer in a block.
      blocks: integer, blocks in the stacked blocks.
      stride1: default 2, stride of the first layer in the first block.
      name: string, stack label.

  Returns:
      Output tensor for the stacked blocks.
  """
  x = block2(x, filters, conv_shortcut=True, name=name + '_block1')
  for i in range(2, blocks):
    x = block2(x, filters, name=name + '_block' + str(i))
  x = block2(x, filters, stride=stride1, name=name + '_block' + str(blocks))
  return x


def block3(x,
           filters,
           kernel_size=3,
           stride=1,
           groups=32,
           conv_shortcut=True,
           name=None):
  """A residual block.

  Args:
    x: input tensor.
    filters: integer, filters of the bottleneck layer.
    kernel_size: default 3, kernel size of the bottleneck layer.
    stride: default 1, stride of the first layer.
    groups: default 32, group size for grouped convolution.
    conv_shortcut: default True, use convolution shortcut if True,
        otherwise identity shortcut.
    name: string, block label.

  Returns:
    Output tensor for the residual block.
  """
  bn_axis = 3 if backend.image_data_format() == 'channels_last' else 1

  if conv_shortcut:
    shortcut = layers.Conv2D(
        (64 // groups) * filters,
        1,
        strides=stride,
        use_bias=False,
        name=name + '_0_conv')(x)
    shortcut = layers.BatchNormalization(
        axis=bn_axis, epsilon=1.001e-5, name=name + '_0_bn')(shortcut)
  else:
    shortcut = x

  x = layers.Conv2D(filters, 1, use_bias=False, name=name + '_1_conv')(x)
  x = layers.BatchNormalization(
      axis=bn_axis, epsilon=1.001e-5, name=name + '_1_bn')(x)
  x = layers.Activation('relu', name=name + '_1_relu')(x)

  c = filters // groups
  x = layers.ZeroPadding2D(padding=((1, 1), (1, 1)), name=name + '_2_pad')(x)
  x = layers.DepthwiseConv2D(
      kernel_size,
      strides=stride,
      depth_multiplier=c,
      use_bias=False,
      name=name + '_2_conv')(x)
  x_shape = backend.shape(x)[:-1]
  x = backend.reshape(x, backend.concatenate([x_shape, (groups, c, c)]))
  x = layers.Lambda(
      lambda x: sum(x[:, :, :, :, i] for i in range(c)),
      name=name + '_2_reduce')(x)
  x = backend.reshape(x, backend.concatenate([x_shape, (filters,)]))
  x = layers.BatchNormalization(
      axis=bn_axis, epsilon=1.001e-5, name=name + '_2_bn')(x)
  x = layers.Activation('relu', name=name + '_2_relu')(x)

  x = layers.Conv2D(
      (64 // groups) * filters, 1, use_bias=False, name=name + '_3_conv')(x)
  x = layers.BatchNormalization(
      axis=bn_axis, epsilon=1.001e-5, name=name + '_3_bn')(x)

  x = layers.Add(name=name + '_add')([shortcut, x])
  x = layers.Activation('relu', name=name + '_out')(x)
  return x


def stack3(x, filters, blocks, stride1=2, groups=32, name=None):
  """A set of stacked residual blocks.

  Args:
    x: input tensor.
    filters: integer, filters of the bottleneck layer in a block.
    blocks: integer, blocks in the stacked blocks.
    stride1: default 2, stride of the first layer in the first block.
    groups: default 32, group size for grouped convolution.
    name: string, stack label.

  Returns:
    Output tensor for the stacked blocks.
  """
  x = block3(x, filters, stride=stride1, groups=groups, name=name + '_block1')
  for i in range(2, blocks + 1):
    x = block3(
        x,
        filters,
        groups=groups,
        conv_shortcut=False,
        name=name + '_block' + str(i))
  return x


@keras_export('keras.applications.resnet50.ResNet50',
              'keras.applications.resnet.ResNet50',
              'keras.applications.ResNet50')
def ResNet50(include_top=True,
             weights='imagenet',
             input_tensor=None,
             input_shape=None,
             pooling=None,
             classes=1000,
             **kwargs):
  """Instantiates the ResNet50 architecture."""

  def stack_fn(x):
    x = stack1(x, 64, 3, stride1=1, name='conv2')
    x = stack1(x, 128, 4, name='conv3')
    x = stack1(x, 256, 6, name='conv4')
    return stack1(x, 512, 3, name='conv5')

  return ResNet(stack_fn, False, True, 'resnet50', include_top, weights,
                input_tensor, input_shape, pooling, classes, **kwargs)


@keras_export('keras.applications.resnet.ResNet101',
              'keras.applications.ResNet101')
def ResNet101(include_top=True,
              weights='imagenet',
              input_tensor=None,
              input_shape=None,
              pooling=None,
              classes=1000,
              **kwargs):
  """Instantiates the ResNet101 architecture."""

  def stack_fn(x):
    x = stack1(x, 64, 3, stride1=1, name='conv2')
    x = stack1(x, 128, 4, name='conv3')
    x = stack1(x, 256, 23, name='conv4')
    return stack1(x, 512, 3, name='conv5')

  return ResNet(stack_fn, False, True, 'resnet101', include_top, weights,
                input_tensor, input_shape, pooling, classes, **kwargs)


@keras_export('keras.applications.resnet.ResNet152',
              'keras.applications.ResNet152')
def ResNet152(include_top=True,
              weights='imagenet',
              input_tensor=None,
              input_shape=None,
              pooling=None,
              classes=1000,
              **kwargs):
  """Instantiates the ResNet152 architecture."""

  def stack_fn(x):
    x = stack1(x, 64, 3, stride1=1, name='conv2')
    x = stack1(x, 128, 8, name='conv3')
    x = stack1(x, 256, 36, name='conv4')
    return stack1(x, 512, 3, name='conv5')

  return ResNet(stack_fn, False, True, 'resnet152', include_top, weights,
                input_tensor, input_shape, pooling, classes, **kwargs)


@keras_export('keras.applications.resnet50.preprocess_input',
              'keras.applications.resnet.preprocess_input')
def preprocess_input(x, data_format=None):
  return imagenet_utils.preprocess_input(
      x, data_format=data_format, mode='caffe')


@keras_export('keras.applications.resnet50.decode_predictions',
              'keras.applications.resnet.decode_predictions')
def decode_predictions(preds, top=5):
  return imagenet_utils.decode_predictions(preds, top=top)


preprocess_input.__doc__ = imagenet_utils.PREPROCESS_INPUT_DOC.format(
    mode='',
    ret=imagenet_utils.PREPROCESS_INPUT_RET_DOC_CAFFE,
    error=imagenet_utils.PREPROCESS_INPUT_ERROR_DOC)
decode_predictions.__doc__ = imagenet_utils.decode_predictions.__doc__

DOC = """

  Reference:
  - [Deep Residual Learning for Image Recognition](
      https://arxiv.org/abs/1512.03385) (CVPR 2015)

  For image classification use cases, see
  [this page for detailed examples](
    https://keras.io/api/applications/#usage-examples-for-image-classification-models).

  For transfer learning use cases, make sure to read the
  [guide to transfer learning & fine-tuning](
    https://keras.io/guides/transfer_learning/).

  Note: each Keras Application expects a specific kind of input preprocessing.
  For ResNet, call `tf.keras.applications.resnet.preprocess_input` on your
  inputs before passing them to the model.
  `resnet.preprocess_input` will convert the input images from RGB to BGR,
  then will zero-center each color channel with respect to the ImageNet dataset,
  without scaling.

  Args:
    include_top: whether to include the fully-connected
      layer at the top of the network.
    weights: one of `None` (random initialization),
      'imagenet' (pre-training on ImageNet),
      or the path to the weights file to be loaded.
    input_tensor: optional Keras tensor (i.e. output of `layers.Input()`)
      to use as image input for the model.
    input_shape: optional shape tuple, only to be specified
      if `include_top` is False (otherwise the input shape
      has to be `(224, 224, 3)` (with `'channels_last'` data format)
      or `(3, 224, 224)` (with `'channels_first'` data format).
      It should have exactly 3 inputs channels,
      and width and height should be no smaller than 32.
      E.g. `(200, 200, 3)` would be one valid value.
    pooling: Optional pooling mode for feature extraction
      when `include_top` is `False`.
      - `None` means that the output of the model will be
          the 4D tensor output of the
          last convolutional block.
      - `avg` means that global average pooling
          will be applied to the output of the
          last convolutional block, and thus
          the output of the model will be a 2D tensor.
      - `max` means that global max pooling will
          be applied.
    classes: optional number of classes to classify images
      into, only to be specified if `include_top` is True, and
      if no `weights` argument is specified.
    classifier_activation: A `str` or callable. The activation function to use
      on the "top" layer. Ignored unless `include_top=True`. Set
      `classifier_activation=None` to return the logits of the "top" layer.
      When loading pretrained weights, `classifier_activation` can only
      be `None` or `"softmax"`.

  Returns:
    A Keras model instance.
"""

setattr(ResNet50, '__doc__', ResNet50.__doc__ + DOC)
setattr(ResNet101, '__doc__', ResNet101.__doc__ + DOC)
setattr(ResNet152, '__doc__', ResNet152.__doc__ + DOC)
